If he has run it hot,the color of the top of the piston should tell the story on thatIf the top of the piston is very dark and burned looking,then he has burned it upMost likely from running the wrong fuel.The top of the piston should be very clean and shinny,almost like new.[8D]Although CEN recommends 30%nitro,I have found that these engines run too hot on 30.If he must run 30%,I wouldnt do it until the motor has run for at least 2 gallons on 20%to make sure its broke in good,but a NX-76 new or broken in by the book will run hot on 30% every time.Most people make the mistake of breaking in one of these engines by the book and figure thats enough,but it actually takes around two gallons to break in one of those[8D]Let me know what you find.